Process and agents for the clear-rinse in mechanical dishwashing

ABSTRACT

PROCESS FOR RINSING OF DISHES IN DISHWASHING MACHINES HAVING ONE OR SEVERAL CLEAR-RINSING CYCLES USING AN AQUEOUS SOLUTION OF AN ADDUCT OF FROM 5 TO 20 MOLS OF ETHYLENE OXIDE AND FROM 1 TO 10 MOLS OF PROPYLENE OXIDE TO ALKANEDIOLS WITH A LINEAR ALKANE CHAIN OF FROM 10 TO 20 CARBON ATOMS AND HAVING VICINAL, NON-TERMINAL HYDROXYLS, AS WELL AS CLEAR-RINSING AGENT COMPOSITIONS FOR USE IN THE PROCESS.

United States Patent 3,775,330 PROCESS AND AGENTS FOR THE CLEAR-RINSE INMECHANICAL DISHWASI-IING Heimold Batka, Dusseldorf-Reishold, and TheodorAltenschiipfer, Dusseldorf-Holthausen, Germany, assignors to Henkel &Cie G.m.b.H., Dusseldorf, Germany No Drawing. Filed Dec. 7, 1971, Ser.No. 205,719 Claims priority, application Germany, Dec. 18, 1970, P 20 62463.9 Int. Cl. Clld N66 US. Cl. 252-89 5 Claims ABSTRACT OF THEDISCLOSURE Process for rinsing of dishes in dishwashing machines havingone or several clear-rising cycles using an aqueous solution of anadduct of from 5 to 20 mols of ethylene oxide and from 1 to mols ofpropylene oxide to alkanediols with a linear alkane chain of from 10 'to20 carbon atoms and having vicinal, non-terminal hydroxyls, as well asclear-rinsing agent compositions for use in the process.

TIIE PRIOR ART In mechanical dishwashing generally two cleaning cycles,usually separated by intermediate rinsing cycles with pure water areused. In the two cleaning cycles, different products are utilized. Inthe first or true cleaning cycle, alkaline-reacting agents are employedfor the loosening and emulsifying of the food residues. In theafter-rinsing or clear-rinsing bath, on the other hand, specialclear-rinsing agents are employed. The latter should possess a goodwetting power and be able to reduce the surface tension of theafter-rinsing water to such a degree that it drains in a film-likemanner from the dishes and leaves no visible deposits, such as limespots or other impurities.

Because of the violent agitation of the liquor in the dishwasher, theseclear-rinsing agents have to be as lowfoaming as possible. It is,however, known that the customary anionic wetting agents, such ashigher-molecularweight alkyl sulfates or alkyl sulfonates or aralkylsulfonates foam too much. In practice, therefore, mostly non-ionictensides based on ethylene oxide adducts to fatty alcohols, alkylphenolsor polypropylene glycols of higher molecular weights are employed. Theseproducts, however, are not sufiiciently low foaming in the concentrationrange, required for a sufficient wetting eifect, and disturbances in therinsing process may occur, because of a too strong foam formation in thedishwasher.

In copending, commonly-assigned US. patent application Ser. No. 205,723,filed concurrently herewith, clearrinsing agents are disclosed based onnon-ionic tensides which are characterized by a content of an adduct offrom 3 to 30 mols of ethylene oxide to alkanediols with a linear alkanechain of from 1 0 to 20 carbon atoms and having vicinal, non-terminalhydroxyls. These products, particularly with a content of more than 5mols of ethylene oxide, are optionally combined with foam-suppressingsubstances of the type of non-ionic alkylene oxide adducts to higheralkanols, alkanediols and alkylphenols.

3,775,330 Patented Nov. 27, 1973 OBJECTS OF THE INVENTION An object ofthe invention is the development of lowfoaming and biologicallydegradable clear-rinsing agents for mechanical dishwashing with a goodWetting and draining effect toward hard surfaces.

Another object of the invention is the development in the process forthe mechanical washing of dishes which comprises subjecting dirty dishesto the action of a Washing solution, subjecting the washed dishes to atleast one clear-rinsing solution and recovering said washed dishes, theimprovement consisting of utilizing an aqueous solution containing from0.01 to 1.0 gm. per liter of an adduct of from 5 to 20 mols of ethyleneoxide and from 1 to 10 mols of propylene oxide to an alkanediol having alinear alkane chain with from 10 to 20 carbon atoms and vicinal,non-terminal hydroxyls, as said at least one clearrinsing solution.

A further object of the present invention is the development oflow-foaming rinsing compositions adapted for dishwashers consistingessentially of (A) an adduct of from 5 to 20 mols of ethylene oxide andfrom 1 to 10 mols of propylene oxide to an alkanediol having a linearalkane chain with from 10 to 20 carbon atoms and vicinal, non-terminalhydroxyls, and (B) a lower organic carboxylic acid having from 2 to 6carbon atoms and sequestering properties toward salts causing waterhardness, wherein the weight ratio between component (A) and component(B) is from 1:02 to 1:3.

A yet further object of the present invention is the development of aclear-rinsing agent concentrate adapted for dishwashers consistingessentially of (1) 20% to by weight of water, (2) from 10% to 60% byweight of an adduct of from 5 to 20 mols of ethylene oxide and from 1 to10 mols of propylene oxide to an alkanediol having a linear alkane chainwith from 10 to 20 carbon atoms and vicinal, non-terminal hydroxyls, (3)from 0 to 40% by weight of a water-miscible lower alcohol and (4) from 0to 40% by weight of a lower organic carboxylic acid having from 2 to 6carbon atoms and sequestering properties toward salts causing waterhardness.

These and other objects of the invention will become more apparent asthe description thereof proceeds.

DESCRIPTION OF THE INVENTION The objects of the invention have beenachieved by the development of clear-rinsing agents for automaticdishwashing based on non-ionic, low-foaming tensides that combine thedesirable properties to a high degree. The clear-rinsing agents of theinvention are adducts of from 5 to 20 mols of ethylene oxide and from 1to 10 mols of propylene oxide to alkanediols with linear alkane chainsof from 10 to 20 carbon atoms, whose hydroxyl groups are non-terminaland vicinal. By non-terminal, such diols are designated that do notpossess any hydroxyl group on a terminal carbon atom.

Such products are distinguished at concentrations giv ing goodclear-rinsing effects, by extreme low-foaming so that a combination withfoam-suppressing substances is not necessary.

For the preparation of the adducts, non-terminal afidiols are utilizedas the starting materials. Such diols are prepared in a known way fromlinear aliphatic olefins with non-terminal double bonds, for instance,by epoxidation with the aid of peracids or hydrogen peroxide and lowercarboxylic acids forming peracids and subsequent saponification of theepoxides. The starting materials are preferably such olefins whosedouble bond is about in the middle of the carbon chain. The productsobtained normally are mixtures of different vicinal diols, whose diolgroups are distributed statistically around a median value with the mainamount in the center of the carbon chain.

The reaction of the ethylene oxide and propylene oxide with the vicinal,non-terminal diols is carried out in a known manner in the presence ofacidic or basic catalysts, preferably with the use of elevatedtemperatures and pressures, first with the desired amount of ethyleneoxide and subsequently with the desired amount of propylene oxide. Inpractice, preferably a two-step process is utilized. In the first steponly 1 mol of ethylene oxide is reacted with 1 mol of the diol or diolmixture. The reaction leads substantially to the formation ofmonoethoxylated diols. The reaction mixture is purified by distillingoff the unreacted diol. In the second reaction the monoethoxylated diolis further reacted by addition of the desired amount of ethylene oxide.Subsequently to the addition of ethylene oxide the further reaction withpropylene oxide is executed in a conventional and known manner. By thistwo-step reaction, preferably, each time one polyalkylene glycol chainper diol group is formed, as substantially only the primary hydroxylgroups, deriving from the first reaction step, react further withethylene oxide and thereafter with the propylene oxide with sufficientspeed. The other secondary hydroxyl groups of the vicinal, non-terminaldiol remain largely unchanged.

Products, suitable in the sense of the invention, are particularlyadducts that contain to mols of ethylene oxide and 3 to 10 mols ofpropylene oxide and in which the molar amounts of the added ethyleneoxide to propylene oxide are in the ratio of 1:0.05 to 2, preferably110.3 to 2. As starting materials diols or diol mixtures of an averagealkane chain length of 12 to 18 carbons, preferably 14 to 16 carbons,are preferred. Examples for suitable substances are the adducts of 5mols of ethylene oxide and 3 mols of propylene oxide or 7 mols ofethylene oxide and 5 mols of propylene oxide or 7 mols of ethylene oxideand 10 mols of propylene oxide to diols or diol mixtures of averagechain lengths of 14 to 16 carbons. The claimed products are extremelylow foaming and exhibit over large concentration ranges, a good drainingand cleardrying effect on various customary kitchenware, such asporcelain plates, cutlery, tableware and particularly on glasses, whichare particularly difiicult in this respect. They are, therefore,extraordinarily suited for the clear rinsing of dishes after a precedingcleaning cycle, for example, with alkaline cleaners. Already inconcentrations of about 0.05 gm./l. a drop-free, filmlike draining ofthe clearrinsing liquor from the dishes is attained. A disturbing foamformation does not occur at these concentrations.

The claimed products or combinations are applied in the clear-rinsingbath in concentrations from about 0.01 to 1.0 gm./l., preferably 0.05 to0.6 gm./l. of active substance. The application concentration depends toa certain degree upon the kind of surface to be cleaned. Particularly,synthetic resin surfaces require a somewhat higher amount ofclear-rinsing agents. The application is effected preferably in the formof aqueous or dilute alcoholic concentrates with contents from 10% to60% by weight of the active components. As alcoholic solvent components,preferably water-miscible lower alcohols such as ethanol, propanol andisopropanol, ethylene glycol, monoethyl ether of ethylene glycol and thelike are uti lized.

If the adducts themselves are liquid, they can also be applied withoutsolvents. The concentrates are appropriately added with the aid Ofautomatic dosing devices, as

are already customary for such purposes, or manually to theclear-rinsing liquor.

The invention also involves, in the process for the mechanical washingof dishes which comprises subjecting dirty dishes to the action of awashing solution, subjecting the washed dishes to at least oneclear-rinsing solution and recovering said washed dishes, theimprovement consisting of utilizing an aqueous solution containing from0.01 to 1.0 gm. per liter of an adduct of from 5 to 20 mols of ethyleneoxide and from 1 to 10 mols of propylene oxide to an alkanediol having alinear alkane chain with from 10 to 20 carbon atoms and vicinal,non-terminal hydroxyls, as said at least one clear-rinsing solution.

If the rinsing is effected with hard water, lower organic carboxylicacids with 2 to 6 carbon atoms may be added to the concentrates or theclear-rinsing liquor for the avoidance of lime incrustations and limehazes on the rinsed dishes. Acids are preferred that are physiologicallyinnocuous and that possess sequestering properties toward the hardnesscausing salts, such as tartaric acid, lactic acid, glycolic acid andparticularly citric acid. The optional addition of acid in theclear-rinsing concentrate amounts to about 10% to 40% by weight.

The low-foaming clear-rinsing agents of the invention are, therefore,optionally low-foaming rinsing compositions adapted for dishwashersconsisting essentially of (A) an adduct of from 5 to 20 mols of ethyleneoxide and from 1 to 10 mols of propylene oxide to an alkanediol having alinear alkane chain with from 10 to 20 carbon atoms and vicinal,non-terminal hydroxyls, and (B) a lower organic carboxylic acid havingfrom 2 to 6 carbon atoms and sequestering properties toward saltscausing water hardness, wherein the weight ratio between component (A)and component (B) is from 1:02 to 1:3.

Essentially where a concentrate is employed in accordance with theinvention, this is a clear-rinsing agent concentrate adapted fordishwashers consisting essentially of (l) 20% to by weight of water, (2)from 10% to 60% by weight of an adduct of from 5 to 20 mols of ethyleneoxide and from 1 to 10 mols of propylene oxide to an alkanediol having alinear alkane chain with from 10 to 20 carbon atoms and vicinal,non-terminal hydroxyls, (3) from 0 to 40% by weight of a water-misciblelower alcohol and (4) from 0 to 40% by weight of a lower organiccarboxylic acid having from 2 to 6 carbon atoms and sequesteringproperties toward salts causing water hardness.

The following specific examples are illustrative of the inventionwithout being limitative in any manner.

EXAMPLES In a test of foaming caused by the rhythmic insertion andwithdrawal of a perforated disk, the foaming behavior of variousclear-rinsing agents of the invention was determined. The results of thetests, given in the following Table I, demonstrates the extraordinarilyfavorable foaming behavior of the claimed agents.

At a dosage level of 1 gm./l. of clear-rinsing agents, aqueous solutionsof the compounds listed in Table I were stamped 20 times in a measuringcylinder with a perforated disk and subsequently the foam height incentimeters after 10, 30 and 60 seconds was recorded. Foaming heightsabove 20 cm. are marked by X. The city water used had a dH (degreesGerman hardness) of 12.

The abbreviations used in the table and examples are:

EO=mols of ethylene oxide.

Pr0=mols of propylene oxide.

C -diol=a vicinal, non-terminal alkanediol with carbon chains with 15,16 and 17 carbon atoms in statistical distribution, average: 16 carbonatoms.

C -diol=a vicinal, non-terminal alkanediol with carbon chains with 13,14 and 15 carbon atoms in statistical distribution, average: 14 carbonatoms.

TABLE I 60 0. Permutit 50 city water treated water 1a 20% Cm-diol plus 7E/3 Pr0 3. 4 1. 9 1. 2 3.0 1. 6 1. 2 1b 20% C1s-dio1 plus 7 EO/& PrO..0. 7 0. 9 0. 9 1. 1 l. 1 1. 1 1c 20% Cu-diol plus 7 EO/10 PrO 0 0 0 0 00 1d 20% Cre-diol plus 7 EO/3 PrO 2 2 1 6 1 6 2 7 1 4 1 4 20% citricacid 1o 20% Cm-diol plus 7 EO/5 PrO 0 5 0 5 o 5 1 o 1 0 1 0 20% citricacid .4 1f 20% Cm-diol plus 7 E0110 Pr 0 0 0 0 0 0 20% citric acid ggg gggf Plus 9 Pro 1. o 1. 0 1. 0 1. a 1. 4 1. 4 2b 50% Cn-d iol plus a EO/5PrO 0 o 0 (L 6 0' 5 5 20% ethanol 2c 20% Cu-diol plus 5 EO/ PrO 0 0 0 00 0 Example 1 A clear-rinsing agent with a good effect for homedishwashing machines as well as for commercial dishwashers has thefollowing composition:

Percent C -dlO1-i-7E0/5PI'0 Water 60 An acidic adjusted after-rinsingagent, particularly for home dishwashers, has the following composition:

Percent C -dio1+7EO/3Pro 20 Citric acid 28 Water 52 The clear-dryingeffect is excellent over a concentration range from 0.2 to 1.0 gm./l.Foaming 1s very low.

Example 3 A neutral clear-rinsing agent that proved particularlysuitable in commercial dishwashing machines with a very high watercirculation has the following composition:

Percent C -diol+5EO/1OPr0 53 Ethanol 20 Water 27 In spite of the highwater circulation, no disturbing foam is developed. The clear-dryingeflect is good.

The preceding specific embodiments are illustrative of the practice ofthe invention. It is to be understood, however, that other expedientsknown to those skilled in the art, or disclosed herein, may be employedwithout departing from the spirit of the invention or the scope of theclaims.

We claim:

1. Low-foaming rinsing concentrates adapted for dishwashers consistingessentially of (A) an adduct of from 5 to 20 mols of ethylene oxide andfrom 1 to 10 mols of propylene oxide to an alkanediol having a linearalkane chain with from 10 to 20 carbon atoms and vicinal, nonterminalhydroxyls, and (B) a lower organic carboxylic acid having from 2 to 6carbon atoms and sequestering properties toward salts causing waterhardness, wherein the weight ratio between component (A) and component(B) is from 1:02 to 1:3 in an aqueous solution containing from 20% to ofwater.

2.. The low-foaming rinsing concentrates of claim 1 wherein said adductis an adduct of from 5 to 10 mols of ethylene oxide and from 3 to 10mols of propylene oxide to an alkanediol having a linear alkane chainwith from 12 to 18 carbon atoms and vicinal, non-terminal hydroxyls.

3. A clear-rinsing agent concentrate adapted for dishwashers consistingessentially of (1) 20% to 90% by weight of water, (2) from 10% to 60% byweight of an adduct of from 5 to 20 mols of ethylene oxide and from 1 to10 mols of propylene oxide to an alkanediol having a linear alkane chainwith from 10 to 20 carbon atoms and vicinal, non-terminal hydroxyls, (3)from 0 to 40% by weight of a water-miscible lower alcohol and (4) from 0to 40% by weight of a lower organic carboxylic acid having from 2 to 6carbon atoms and sequestering properties toward salts causing waterhardness.

4. The clear-rinsing agent concentrate of claim 3 wherein said adduct isan adduct of from 5 to 10 mols of ethylene oxide and from 3 to 10 molsof propylene oxide to an alkanediol having a linear alkane chain withfrom 12 to 18 carbon atoms and vicinal, non-terminal hydroxyls.

5. The clear-rinsing agent concentrate of claim 3 wherein said component(4) is present in an amount of from 10% to 40% by weight.

References Cited UNITED STATES PATENTS 3,382,178 5/1968 Lissant et al.25289 UX 3,563,901 2/ 1971 Crotty 252136 2,584,017 1/ 1952 Dvorkovitz etal. 25289 3,082,172 3/1963 Temple et al. 25289 3,503,885 3/1970 Wedell25289 3,592,774 7/1971 Altenschopfer 25289 WILLIAM E. SCHULZ, PrimaryExaminer US. Cl. X.R. 13426

